Preparation of neutral or alkaline precipitating liquids



Patented :J l 18 r UNITED STATES.

,ALBEBT BODMER, or WATTWIL,

or ARBON, SWITZERLAND, ACoBPoa TIoN or SWITZERLAND PREPARATION or NEUTZRAL QRALKALI N E-PRECIPITATING LIQUiDS "PA OFFICE v SWITZERLAND, ASSIGNOR To NOVASETA ,A. 0. Anson,

No Drawing. Application 'filed October 4, 1929; Serial No. 397,455, and in switzer langl oeto ers, 192811 It is known that in the manufacture of artificial silk the action of dissolved gases in precipitating baths is detrimentalto the formation of the thread. Especially when 5 using running liquids the gas bubbles formed cause a breakage of th'e'fibrillas. To avoid this it was suggested to withdraw the gases be heated continuouslyto a high temperature.

For-instance, to withdraw 50% ofthe dissolved gases the liquid has to be heated up to 80 C. which however may prove to be disadvantageous. I

' Nowit has been found that a precipitating bath consisting of meteoric water, which always contains dissolved air and carbonic acid can be used by adding asmall quantity oflalkali hydroxide and alkali hydrosulfite,

which bind the free carbonic acid and the dissolved oxygen. Experience shows that when working according to this method generally two-thirds of. the total quantity of the 'dissolved gases can be-neut'ralized. The part of the dissolved gas still remaining consists in the main of nitrogen and is notdetrimental I in the spinningprocess. If for'instance well water, containing42 cubic centimetres dissolved gas to the liter (the dissolved gas consisting of45% carbonic acid, 17 oxygen s y and nitrogen) is combined in the reserve tank with 0,18 grammes: caustic soda and 0,09 grammes h drosulfite q of H (NagS O to the liter, this solution can be well used as ap'recipitating bath. Variations in the combination of the gases dissolved in water are quite natural; by means ofthe ex treme proportions attained howevera medium s I s can be determined and the additions adjusted accordingly A precipitatingbath thusprepared is practically neutral,'it'can however be changedinto an alkaline bath in any de-f' f .sirable nanneror any desirable additioncan be given excepting means of an'acid character,

Having thus described 'myinve'ntion, what Patent is fi 'Iclaini as new and desire to secure byLetters 1; A process for preparing a precipitating bath of the kind described, whichcom y prises mixing with the precipitating bath a 1 caustic alkali to remove carbon dioxide and) an alkali metal hydroesulfite to remove the v dissolved'oxygen from the precipitating bath.

2. A neutral or alkaline precipitating soluucts of alkali hydroxide and falkali hydrolsulfite with carbon dioxideand free oxygen in thewater employedfor precipitation;

v ALBERT BODMER,

tionlof the kind described substantially'free from carbon dioxide'and oxygenand con- 5M 1, taming a small quantity ofithe reactionprod- 

